Bob Pease on the New LM4562 - Page 3 - diyAudio
Go Back   Home > Forums > Design & Build > Parts

Parts Where to get, and how to make the best bits. PCB's, caps, transformers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 13th September 2006, 01:12 PM   #21
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
$2.43/1k for SOIC -- about 1/2 the cost of AD797AR
  Reply With Quote
Old 13th September 2006, 05:16 PM   #22
forr is offline forr  France
diyAudio Member
 
forr's Avatar
 
Join Date: Dec 2004
Location: Next door
I'd like to see the internal schematics of the LM4562.
  Reply With Quote
Old 13th September 2006, 07:42 PM   #23
diyAudio Member
 
wrenchone's Avatar
 
Join Date: Feb 2004
Location: Silicon Valley
Given the rise in THD and IM at low levels (though it's still low), I wonder if the LM4562 would benefit from current source loading to force the output into Class A?
  Reply With Quote
Old 13th September 2006, 07:56 PM   #24
diyAudio Member
 
wrenchone's Avatar
 
Join Date: Feb 2004
Location: Silicon Valley
Just for perspective, the typical input bias current for the LM4562 is 5X less than the LT1115, and 20X less than the NE5532. In addition to reducing noise using MM cartridges (0.5-1H typical inductances!), there is more freedom choosing feedback components without having to worry so much about extra offset voltage.
  Reply With Quote
Old 13th September 2006, 08:08 PM   #25
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Quote:
Originally posted by wrenchone
Given the rise in THD and IM at low levels (though it's still low), I wonder if the LM4562 would benefit from current source loading to force the output into Class A?
Is it really distortion or is it noise?
__________________
The more you pay for it, the less inclined you are to doubt it.- George Smiley
  Reply With Quote
Old 13th September 2006, 08:22 PM   #26
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Quote:
Originally posted by SY


Is it really distortion or is it noise?

If you look at the open loop gain vs frequency, it is ugly. Open loop bandwidth is 10Hz or so! Yes, that Herz, NOT kiloHerz!

So, the feedback in a closed loop config starts to loose effectiveness from 10Hz upwards, and that causes the rises of the hf THD once the harmonics come out of the noise.
The low THD of this thing is NOT due to its high ol bandwidth, but in some way they have made this thing extremely linear open loop.

Jan Didden
__________________
If you don't change your beliefs, your life will be like this forever. Is that good news? - W. S. Maugham
Check out Linear Audio!
  Reply With Quote
Old 13th September 2006, 08:28 PM   #27
diyAudio Member
 
wrenchone's Avatar
 
Join Date: Feb 2004
Location: Silicon Valley
Has anybody found a distributor for this part yet? I checked Digi-Key, Newark, Allied, Mouser, and Arrow. Either there is no hit for the LM4562, or in the case of Arrow, a hit but no stock. I tried Future, but their search just hangs up for 10-15 min without spitting out any results - a bad omen in any case.
  Reply With Quote
Old 13th September 2006, 08:36 PM   #28
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Quote:
Originally posted by janneman



...the feedback in a closed loop config starts to loose effectiveness from 10Hz upwards, and that causes the rises of the hf THD once the harmonics come out of the noise.
Well, looking at THD vs frequncy, it's pretty flat until you reach 10k, where it starts to rise. OTOH, the THD vs level shows the distortion rising monotonically with decreasing level. That's what suggested noise to me.
__________________
The more you pay for it, the less inclined you are to doubt it.- George Smiley
  Reply With Quote
Old 13th September 2006, 08:41 PM   #29
diyAudio Member
 
wrenchone's Avatar
 
Join Date: Feb 2004
Location: Silicon Valley
The LT1115 has similar open loop bandwidth characteristics to the LM4562 and similar behavior of IM and THD vs amplitude. Linear shows current source loading in their application circuit for an RIAA preamp. Makes me wonder... BTW, given the extremely high open loop gain of both parts, I wouldn't expect an open loop BW of much higher than 10Hz in any case.
  Reply With Quote
Old 13th September 2006, 09:09 PM   #30
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Quote:
Originally posted by SY


Well, looking at THD vs frequncy, it's pretty flat until you reach 10k, where it starts to rise. OTOH, the THD vs level shows the distortion rising monotonically with decreasing level. That's what suggested noise to me.

Stuart, yes, I understood your post that you suggested that the rise of THD with freq was due to noise, which isn't the case.

Agree with the quoted post. The rise of THD above 10k is because at that freq (due to decreasing feedback effectiveness) the THD starts to rise above the noise. I would guess that if we could see below the noise the THD would steadily decrease with freq to 10Hz and flatten out from there downwards...

Jan Didden
__________________
If you don't change your beliefs, your life will be like this forever. Is that good news? - W. S. Maugham
Check out Linear Audio!
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



New To Site? Need Help?

All times are GMT. The time now is 12:28 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2